SolarReserve has a solar thermal project planned for Port Augusta, similar to its Crescent Dunes project in Nevada.
Photograph: Pedro Alvarez for the Observer

When it comes to South Australia’s radical plans for energy storage to support its power network, all roads lead to Port Augusta – or all transmission lines, that is.

Proponents of projects that include energy storage have converged on this small outback city perched on the top of the Spencer Gulf – but why here and why now?

The now is easily explained. These companies are seeking to be part of the energy infrastructure revolution promised by the South Australian government, which has recognised that more energy storage is essential to complement the intermittent wind farms and solar plants replacing the state’s ageing coal and gas plants.

The proposals are a diverse grab bag of technologies that include battery storage setups either standalone or built into solar PV or gas-fired power plants, a solar thermal tower that uses molten salt to store energy and a pumped hydro project.

The transformation underway in the state has even caught the attention of billionaire Tesla co-founder Elon Musk, although the site for his 100MW South Australian battery storage plan – which he promised on Twitter he could roll out within 100 days or it is free – has either not been chosen or publicly announced.

The West Australian company Carnegie Clean Energy is another firm planning battery storage for South Australia and Lyon Solar in partnership with American giant AES Energy Storage is also working on such a system.

Hugh Saddler, honorary associate professor at the ANU Centre for Climate Economics and Policy, says there are plenty of reasons why so many projects are located at Port Augusta – and why Tesla ought to consider the place. “What Port Augusta has got is a great big node on the national energy market – four high-voltage transmission lines converging on the town,” he says. “It also has a skilled workforce of electrical technicians from the recently closed coal plant, not to mention cheap land.”

Spencer Gulf pumped hydro project – EnergyAustralia

Long before Tesla’s battery storage systems were a twinkle in Musk’s eye, pumped hydro has been acting as a store for energy. The process involves pumping water from one reservoir at the base of a hill to another at the top and releasing that water back below to generate power.

It is complementary to other renewables in that wind and solar farms can provide the power to pump the water uphill when the wind is blowing and the sun is shining and, when they aren’t generating electricity, the water can be released to make up for the shortfall.

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EnergyAustralia’s spokesman, Brendan Hennessy, says the company and partners Melbourne Energy Institute and Arup Group have engaged in a feasibility study on the prospect of a pumped hydroelectric project but using seawater instead of the freshwater that has been put to such purposes for decades.

“The proposed site on the northern end of the Spencer Gulf has 300m of elevation and is within 2km of the coast, close to high-voltage transmission lines,” he says.

The company claims the project would be able to produce around 100 megawatts (MW) of electricity with six-to-eight hours of storage, the biggest such project in the world. EnergyAustralia estimates construction would take roughly two years and that it could provide power by the end of 2020.

Big battery project – Zen Energy

Ever since Musk’s tweets caught the attention of Australia’s most senior politicians, the South Australian company Zen Energy has been jumping up and and down pointing out that it is already set up and ready to roll out battery storage. Its Big Battery Project is exactly what it says it is but Zen Energy is yet to decide exactly how big. The company is examining the possibility of a 100MW version and a 150MW option.

The company has a number of solar projects in the Upper Spencer Gulf region and believes a battery storage project would help to stabilise its solar assets and the broader South Australian grid. The company has also formed a partnership with the South Australian gas giant Santos to roll out battery storage systems at gas processing sites.

Zen Energy’s chairman, Ross Garnaut, grumbled to the Guardian that “in this Trump era, we have a world where nothing is real until an American billionaire tweets about it”.

Solar thermal project – SolarReserve

American company Solar Reserve is seeking to capitalise on Port Augusta’s average of 300 days of sunshine a year by rolling out 10,000 mirrors reflecting the sun on to an enormous central tower standing in the middle. The energy generated by the $650m project would be stored in molten salt, meaning the tower could continue providing electricity at night or even on a rainy day – not that Port Augusta has many of those.

Solar Reserve has a track record in solar thermal, already operating the 110MW Crescent Dunes project in Nevada and recently announcing a 450MW tower for Chile.

The technology has been proven to work around Port Augusta already – a similar solar tower was built for the town’s Sundrop Farms project – a 150m tall tower surrounded by mirrors, used for heating and cooling a greenhouse that produces 15,000 tonnes of tomatoes a year.

Solastor Australia has also proposed a $1.2bn solar thermal tower for the town.

Bungala solar PV and storage project – Reach Solar Energy

Located 7km north-east of Port Augusta on a former ostrich farm, Reach Solar Energy is proposing a $660m solar array with an energy storage system built into the development.

The staged construction of the project, which would be of the more common solar PV plant variety rather than solar thermal, would begin with a 100MW single-axis tracking array with plans to add a further 200MW of capacity.

The project is the brainchild of former executives from the coal sector who recognised that the closure of Port Augusta’s northern coal-fired power plant in 2016 meant there was a workforce of skilled electrical technicians and spare capacity on the transmission infrastructure just waiting to be put to use.

If it goes ahead, the project is expected to supply enough electricity to power over 120,000 homes but the capacity of the planned storage component has not been revealed.